Adriamycin-induced decrease of myocardial contraction reserve in rats treated with dobutamine

Doxorubicin-induced cardiac mitochondrionopathy

Doxorubicin (Adriamycin) is a potent and broad-spectrum antineoplastic agent prescribed for the treatment of a variety of cancers, including both solid tumours and leukaemias. Unfortunately, despite its broad effectiveness, long-term therapy with doxorubicin is associated with a high incidence of a cumulative and irreversible dilated cardiomyopathy. Numerous mechanisms have been proposed to account for this toxicity. Although there is general consensus that doxorubicin undergoes redox cycling to generate free radicals that are responsible for mediating the various cytopathologies associated with drug exposure, the source and subcellular targets continue to be debated. This short review provides a synopsis of the evidence implicating cardiac mitochondria as key intracellular targets, both as sites of generation of highly reactive free radical intermediates as well as targets for the interference with cell calcium regulation and bioenergetic failure that are hallmarks of doxorubicin-induced cardiac failure.

Effect of low-dose doxorubicin on calcium content and norepinephrine response in rat aorta

Doxorubicin (DXR) is a common antineoplastic agent whose clinical utility is limited by development of a dose-related cardiomyopathy. Recent studies demonstrating DXR toxicity in skeletal muscle suggest that this compound may in fact be a general depressant of muscle function. Although previous studies have reported possible indirect actions of DXR on blood vessels, we have investigated the direct effects of this agent on vascular smooth muscle. Chronic, low-dose treatment of rats with intraperitoneal DXR (12 mg/kg total dose over 4 weeks) had no significant effect on body or heart weight, left ventricular water or calcium content, or aortic water or calcium content. Contractile responses to norepinephrine of thoracic aortic strips taken from DXR-treated rats were attenuated by this treatment, and sensitivity (EC50) of these strips to norepinephrine was significantly reduced compared to controls. These results suggest that DXR may have physiological effects on vascular smooth muscle function at doses which produce no signs of toxicity in cardiac muscle.